This is a guest post from Simon Grimm, speaker and educator at Ionic Academy. Simon writes about Ionic frequently on his blog Devdactic.

With the development of Ionic apps comes the promise that your code will run on various platforms and screen sizes once it’s ready. While this can work and look fine on your targeted devices out of the box, it might not at first for everyone.

In this post, we’ll take a look at 4 areas to keep an eye on – especially if you plan to ship your Ionic app both as a website (or perhaps PWA?) and also as a native mobile app (perhaps even on phone and tablet devices).

Everything we need is already built into Ionic, but sometimes it’s easy to forget about all the awesomeness. So let’s get started with a tiny base for our examples!

App Starting Template Setup

For this article run the command below to start a new Ionic app with the side menu template:

ionic start devdacticResponsive sideMenu

It’s a super basic app with just 2 pages and a side menu (otherwise the name would be kinda bad) but we also need to make HTTP calls, therefore we use the new HttpClient which is available since Angular 5 and Ionic 3.9.0.

That’s all we’ll need for our examples, so now let’s dive into our areas.

1. Responsive Grid Layout

Most Ionic components already adapt to screen changes and look good across various sizes. However, having something like a list item full size or an Ionic Card displayed full width on my large iMac screen kills my eyes.

If you need your app to look good on a small device and in a desktop web browser, you’ll need to make it as responsive as possible. And what’s better then using the Ionic Grid layout system?

But first we need some data we can display inside a list, so let’s add a simple HTTP call to your pages/home/home.ts like this:

Now we have an array of users from the Randomuser API which we can display as cards. You could make this as simple iteration without any further testing, but if you’re serious about your design (which, of course you are!), you’ll want to make sure to test different sizes and breakpoints.

A breakpoint is a predefined value at which your design snaps from one category to the next. If your screen is smaller than 576px, you fall into the smallest category which is xs. However, at 577px your design will get the sm category applied, so you must prepare your design to also look good there, and at later breakpoints as well.

With Ionic, we can use the row and column system plus the breakpoints to build interfaces that look great across different platforms and adapt to display the best and most intuitive interface to the user.

One Ionic row offers 12 units space for columns, so each column can take an amount of those 12. If your row takes 12 units, it means the row is already full and the next column will be displayed in the following row.

The syntax for the column isn’t immediately obvious, so let’s dive deeper into what it actually means:

col-12: If no other rules match, the column will take all 12 units (greedy column!)col-md-4: At a minimum width of 768px, each column will only use 4 units. This means, a row can now handle 3 columnscol-lg-3: As the screen gets bigger than 992px, a column only needs 3 units which means the row how holds 4 columnscol-xl-2: On the largest screens (1200px+), a column only needs 2 units and a row will display 6 columns

In our example, a column always holds a card, so the design ranges from seeing only 1 card to 6 cards maximum (seen below).

Using a decent flexible layout is definitely mandatory if your app is going to run on multiple platforms and screen sizes. If you don’t invest time into doing this, your app might scare off potential users because it just looks odd.

There’s a lot more to the Grid like setting your own breakpoints, reordering columns, and more so go check it out!

2. CSS Media Queries

While we can’t really accredit this one directly to Ionic, we are still lucky that Ionic bets strongly on the Web and we can thus take advantage of languages like CSS, which most of us have all learned years ago.

Just like the grid layout, we can make use of breakpoints here as well by using @media and different sizes to change part of our UI.

In a recent app, we needed an ion-fabbutton at the top right corner on the web version as it was too hard to spot when it was at the far bottom right corner. However, on a mobile version of your app users are already familiar with having the button floating above lists at the bottom right.

This means the element needs exist in completely different places depending on screen size (and this is a simple element).

One way to achieve this is by having the element there twice, but only displaying it when the media query of your CSS matches. To do this, add the Fab button to your your pages/home/home.html after the list we already have: